This proposal is responsive to RFA-MH-09-170, the Recovery Act Limited Competition: Research to Address the Heterogeneity in Autism Spectrum Disorders (R01). As noted in the RFA, Autism spectrum disorders (ASD) form a very heterogeneous group: over 30 distinct genes have been identified as either causing or contributing to the cause of autism. To better understand how such a diverse array of genes can cause similar ASD phenotypes, we searched for the binding partners of proteins encoded by autism-associated genes and developed an autism protein interaction network (an "interactome") that contains over 900 protein interactions, many of which are novel. One of the most exciting discoveries unveiled by this interactome is the finding that there are three "hub" proteins that are centers for interaction: FXR1, SHANK3, and TSC1. Moreover, SHANK3 interacts with two distinct classes of proteins: one involved in synapse structure, the other involved in RNA metabolism and translation. This latter class connects SHANK3 to the Fragile X protein (FMRP) and its paralogs (FXR1 and 2) as well as the tuberous sclerosis complex proteins (TSC1 and TSC2). Based in part on these findings, we hypothesize that there are shared pathogenic mechanisms amongst various ASD, one of which centers on synapse maintenance and plasticity. We propose that SHANK3 plays two distinct roles at the synapse, one involving synapse organization and maintenance and the other involving local RNA translation at the synapse. To gain insight into key mechanisms underlying ASD pathogenesis, we will identify and characterize the native SHANK3 complexes at the synapse in vivo. To accomplish this, we will generate knock-in mice that tag the SHANK3 protein to permit in vivo purification of SHANK3-associated complexes. We will examine SHANK3 native complexes to determine whether there are distinct classes of SHANK3 protein complexes and the type of proteins in these sub-complexes. We will generate mice that either black or over-express Shank3 and we will characterize these Shank3 mouse models. In addition we will analyze behavioral, anatomical, and physiological consequences of modulating Shank3 expression in mice lacking FXR genes. Detailed behavioral and biochemical studies will allow us to establish a functional relationship between SHANK3 and FXR proteins in vivo and provide a foundation for detailed mechanistic studies that should benefit a broad population of ASD patients. PUBLIC HEALTH RELEVANCE: Autism is a heterogeneous disorder caused by mutations in different genes and is considered a major public health problem given the estimated prevalence of 1 in 150-200 children. We discovered that some autism- causing proteins interact with the same partners suggesting that there are shared pathways that lead to autism. In this grant, we will characterize some common pathways leading to autism, which would be of public health relevance because our studies will help many types of autism rather than one or two subtypes.